Hydrogen peroxide concentration measurement system and hydrogen peroxide concentration measurement method

Abstract

In a hydrogen peroxide concentration measurement system according to the present invention, a specimen water collecting pipe 3 is branched into a first passage 4 and a second passage 5, and the first passage 4 is switchable between a dissolved oxygen concentration measurement flow channel 7 and a first circulation flow channel 9. Moreover, the second passage 5 is switchable between a hydrogen peroxide decomposition flow channel 11 and a second circulation flow channel 13. Further, the dissolved oxygen concentration measurement flow channel 7 is switchable between a discharge pipe 14 and the second circulation flow channel 13. Furthermore, the hydrogen peroxide decomposition flow channel 11 is switchable between the discharge pipe 14 and the first circulation flow channel 9. Consequently, specimen water W flows to be switchable between continuously flowing from a dissolved oxygen concentration meter 8 to a catalyst resin column 12 and continuously flowing from the catalyst resin column 12 to the dissolved oxygen concentration meter 8. This hydrogen peroxide concentration measurement system makes it possible to shorten the time until a measured value after the switching of the measuring system is stabilized and reduce the consumption of the specimen water.

Description

Hydrogen peroxide concentration measurement system and hydrogen peroxide concentration measurement method

[0001] The present invention relates to a measurement system and a measurement method for measuring the concentration of a small amount of hydrogen peroxide in a sample water such as pure water or ultrapure water.

[0002] Conventionally, ultrapure water used in the semiconductor and other electronics industries is produced by treating raw water in an ultrapure water production system that is composed of a pretreatment system, a primary pure water production system, and a subsystem (secondary pure water production system) that treats the primary pure water.

[0003] In the manufacturing process of ultrapure water for the electronics industry, hydrogen peroxide is a very important factor in the ultrapure water supply management. For example, copper, a typical wiring metal, corrodes with hydrogen peroxide at a concentration of a few mg / L, affecting surface flatness and dissolving, which affects the electrical characteristics of semiconductor products and reduces yield. On the other hand, it is known that hydrogen peroxide is generated by ultraviolet irradiation equipment, which is installed in pure water and ultrapure water manufacturing facilities to decompose organic matter. For this reason, it is necessary to analyze (monitor) the hydrogen peroxide concentration.

[0004] Conventionally, methods for analyzing the concentration of hydrogen peroxide have been generally known, such as methods using test paper or test reagents, colorimetry, and oxidation-reduction titration. However, analyzing the concentration of hydrogen peroxide in pure water or ultrapure water production facilities requires microanalysis with analytical values ​​at the mg / L level. Of the various analytical methods mentioned above, methods using test paper or test reagents have difficulty in measuring analytical values ​​at the mg / L level.

[0005] In addition, colorimetry and redox titration require complicated colorimetric and titration procedures, and are difficult to perform in-line automated analysis, making them unsuitable for pure water or ultrapure water production facilities where human intervention is to be minimized. Furthermore, because they require reagents, costs are high due to the cost of chemicals, maintenance, and wastewater treatment after analysis.

[0006] A known hydrogen peroxide analysis system, capable of easily and sensitively analyzing trace amounts of hydrogen peroxide in water, uses a dissolved oxygen concentration meter to calculate the hydrogen peroxide concentration in sample water, as shown in Figures 4 and 5. In this system, a sample water sampling pipe 33 is connected to a predetermined location in a water passage 32 connected to a supply source 31 of treated water (sample water) W in a water treatment process. The sample water sampling pipe 33 branches into a first path 34 and a second path 35, and then merges again at a junction 36, where a dissolved oxygen concentration meter 37 is provided as a dissolved oxygen measuring means. A catalyst resin column 38 serving as a hydrogen peroxide decomposition means is provided in the second path 35. Reference numeral 39 denotes a first on-off valve for the first path 34, and reference numeral 40 denotes a second on-off valve for the second path 35. In the figures, the flow of liquid is indicated by bold lines.

[0007] In the hydrogen peroxide analysis system described above, first, as shown in Figure 4, the first on-off valve 39 is opened and the second on-off valve 40 is closed, and the sample water W is supplied to the first path 34, and the dissolved oxygen concentration of the sample water W is measured with the dissolved oxygen concentration meter 37 (sample water measurement step). Next, as shown in Figure 5, the first on-off valve 39 is closed and the second on-off valve 40 is opened, and the sample water W is supplied to the second path 35, and the dissolved oxygen concentration in the treated water W1 by the catalyst resin column 38 is measured (treated water measurement step).

[0008] The hydrogen peroxide concentration in the sample water W is determined from the measured dissolved oxygen concentrations of the sample water W and the treated water W1 as follows. First, the hydrogen peroxide contained in the sample water W introduced into the catalyst resin column 38 is decomposed to generate oxygen as shown in the following formula (1). The generated oxygen then dissolves in the water and becomes dissolved oxygen. 2H ２ O ２ → 2H ２ O + O ２ ...(1)

[0009] Here, if the dissolved oxygen concentration value in the sample water W (sample water DO) is M1 and the dissolved oxygen concentration value in the treated water W1 obtained in the treated water measurement step (treated water DO) is M2, the difference between the dissolved oxygen concentrations in the treated water W1 and the sample water W is (M2 - M1), so the hydrogen peroxide concentration in the sample water W can be calculated using the following formula (2): (M2 - M1) x (68 / 32) ... (2) (Here, 68 is the molecular weight of hydrogen peroxide on the left side of formula (1) (double since there are two molecules), and 32 is the molecular weight of oxygen on the right side of formula (1). The units on the left side are the same as the units of DO on the right side.)

[0010] 4 and 5 has high measurement accuracy, but uses a single dissolved oxygen concentration meter to alternately measure the dissolved oxygen concentrations in the sample water W and the treated water W1 to calculate the hydrogen peroxide concentration in the sample water W. However, after switching between the measurement systems for the sample water W and the treated water W1, it takes time for the measured dissolved oxygen concentration to stabilize, and during that time it is not possible to calculate the hydrogen peroxide concentration.

[0011] Therefore, Patent Document 1 proposes a hydrogen peroxide analyzing system as shown in Figures 6 and 7. In this system, a sample water sampling pipe 53 is connected to a predetermined location of a water passage 52 that communicates with a supply source 51 of treated water (sample water) W in a water treatment process. The sample water sampling pipe 53 branches into a first path 54 and a second path 58. The downstream portion of the first path 54 serves as a dissolved oxygen concentration measuring section 55, which is equipped with a dissolved oxygen concentration meter 56 and has a first opening / closing valve 57 provided upstream of the dissolved oxygen concentration measuring section 55. The downstream portion of the second path 58 serves as a discharge port 59, and a catalyst resin column 60 is provided upstream of the second path 58. A second opening / closing valve 61 is provided downstream of the catalyst resin column 60. A first communication pipe 62 having a first communication valve 63 is connected, connecting the upstream side of the first opening / closing valve 57 of the first path 54 to the downstream side of the second opening / closing valve 61 of the second path 58, and a second communication pipe 64 having a second communication valve 65 is connected, connecting the upstream side of the second opening / closing valve 61 of the second path 58 to the upstream side of the first opening / closing valve 57 of the first path 54.

[0012] In the hydrogen peroxide analyzing system described above, first, as shown in FIG. 6 , first on-off valve 57 and second on-off valve 61 are opened, and first communication valve 63 and second communication valve 65 are closed. With this, sample water W is supplied from sample water sampling tube 53 to first path 54 and second path 58, and the dissolved oxygen concentration of sample water W flowing through first path 54 is measured with dissolved oxygen concentration meter 56. At this time, sample water W continues to flow through second path 58 to catalyst resin column 60 and is discharged directly from discharge port 59. Next, as shown in FIG. 7 , first on-off valve 57 and second on-off valve 61 are closed, and first communication pipe 62 and second communication pipe 64 are opened. With this, sample water W is supplied from sample water sampling tube 53 to first path 54 and second path 58. As a result, the sample water W flowing through the second path 58 is treated in the catalyst resin column 60, and the treated water W1 passes through the second communication pipe 64 and is passed from the dissolved oxygen concentration measuring section 55 of the first path 53 to the dissolved oxygen concentration meter 56, where the dissolved oxygen concentration is measured. The hydrogen peroxide concentration in the sample water W is then calculated from the measured dissolved oxygen concentrations of the sample water W and the treated water W1. At this time, the sample water W in the first path 54 is discharged from the discharge section 59 via the first communication pipe 62.

[0013] The hydrogen peroxide concentration in the sample water W is then calculated from the measured dissolved oxygen concentrations in the sample water W and the treated water W1. Since the sample water W is constantly flowing through the catalyst resin column 60, the dissolved oxygen concentration in the treated water W1 can be measured with good initial rise.

[0014] Furthermore, Patent Document 2 proposes a hydrogen peroxide analysis system as shown in Figures 8 to 10. In this system, a sample water sampling pipe 73 is connected to a predetermined location on a water passage 72 that is connected to a supply source 71 of treated water (sample water) W in a water treatment process. The sample water sampling pipe 73 branches into a first path 74 and a second path 77. A first dissolved oxygen concentration meter 75 is disposed downstream of the first path 74, and a first open / close valve 76 is provided upstream of the first dissolved oxygen concentration meter 75. A catalyst resin column 78 is provided upstream of the second path 77, while a second dissolved oxygen concentration meter 79 is disposed downstream of the second path 77. A second open / close valve 80 is provided between the catalyst resin column 78 and the second dissolved oxygen concentration meter 79. A communication pipe 81 having a communication valve 82 is connected between the first path 74 downstream of the first open / close valve 76 and the second path 77 downstream of the second open / close valve 80.

[0015] 8 , first, as shown in FIG. 8 , first open / close valve 76 and second open / close valve 80 are opened, and communication valve 82 is closed. Then, sample water W is supplied from sample water collection pipe 73 to first path 74 and second path 77, and the dissolved oxygen concentration of sample water W in first path 74 is measured directly by first dissolved oxygen concentration meter 75. Meanwhile, sample water W in second path 77 is treated in catalyst resin column 78, and the dissolved oxygen concentration of treated water W1 is measured by second dissolved oxygen concentration meter 79.

[0016] 9, by closing the second on-off valve 80 and opening the communication valve 82, the dissolved oxygen concentration of the sample water W can be measured by the first dissolved oxygen concentration meter 75 and also by the second dissolved oxygen concentration meter 79. Furthermore, by closing the first on-off valve 76 and opening the communication valve 82 as shown in FIG. 10, the dissolved oxygen concentration of the treated water W1 treated in the catalyst resin column 78 can be measured by the first dissolved oxygen concentration meter 75 and also by the second dissolved oxygen concentration meter 79.

[0017] The hydrogen peroxide concentration in the sample water W is then calculated from the measured dissolved oxygen concentrations of the sample water W and the treated water W1. In this case, the dissolved oxygen concentration of the sample water W is measured by the first dissolved oxygen concentration meter 75 and also by the second dissolved oxygen concentration meter 79, and the dissolved oxygen concentration of the treated water W1 is measured by the first dissolved oxygen concentration meter 75 and also by the second dissolved oxygen concentration meter 79, thereby correcting errors due to individual differences in the dissolved oxygen concentration meters, allowing the dissolved oxygen concentrations of the sample water W and the treated water W1 to be measured accurately, and ultimately making it possible to accurately calculate the hydrogen peroxide concentration in the sample water W.

[0018] JP 2019-144143 A JP 2019-132677 A

[0019] However, in the hydrogen peroxide concentration measurement system described in Patent Document 1, although the start-up of detection can be accelerated by supplying sample water W even when catalyst resin is not used, during measurement, sample water W is constantly circulating through both first path 54 and second path 58, so that twice the amount of sample water W needs to be collected from sample water collection tube 53, which poses problems such as the risk of water leakage entering and exiting the instrument and increased consumption of sample water W.

[0020] In addition, the hydrogen peroxide concentration measurement system described in Patent Document 2 uses dissolved oxygen concentration meters 75, 79 on both the sample water W and the treated water W (catalyst resin column 78) side, so that the hydrogen peroxide concentrations of the sample water W and the treated water W1 can be measured at all times. However, there are problems in that not only do two dissolved oxygen concentration meters need to be used, but also a transmission is required to correct errors between the dissolved oxygen concentration meters.

[0021] The present invention has been made in consideration of the above-mentioned problems, and aims to provide a hydrogen peroxide concentration measurement system and a hydrogen peroxide concentration measurement method that can shorten the time until the measurement value stabilizes after switching the measurement system and consumes little sample water.

[0022] In order to solve the above problems, the present invention first provides a hydrogen peroxide concentration measurement system for measuring the concentration of hydrogen peroxide in sample water sampled at a predetermined position in a water passage in a water treatment process, the system comprising: a sample water sampling tube for sampling the sample water; the sample water sampling tube branching into a first path and a second path; the first path being switchably provided with a dissolved oxygen concentration measurement flow path having a dissolved oxygen concentration measurement means and a first circulation flow path; the second path being switchably provided with a hydrogen peroxide decomposition flow path having a hydrogen peroxide decomposition means and a second circulation flow path; the hydrogen peroxide decomposition flow path being switchably branched between a discharge pipe and the first circulation flow path, while the dissolved oxygen concentration measurement flow path being switchably branched between a discharge pipe and the second circulation flow path; and the sample water is changeable between flowing continuously from the dissolved oxygen concentration measurement means to the hydrogen peroxide decomposition means or flowing continuously from the hydrogen peroxide decomposition means to the dissolved oxygen concentration measurement means (Invention 1).

[0023] According to this invention (Invention 1), the sample water is not diverted and supplied, but is instead circulated through the oxygen concentration measuring means, where the dissolved oxygen concentration of the sample water is measured, and then circulated through the hydrogen peroxide decomposition means and discharged. The sample water is then circulated from the dissolved oxygen concentration measuring means to the hydrogen peroxide decomposition means, where the dissolved oxygen concentration of the sample water (treated water) treated by the hydrogen peroxide decomposition means is measured. The hydrogen peroxide concentration in the sample water can then be calculated from the dissolved oxygen concentrations of the sample water and the treated water. This results in a system that uses less sample water and has a stable start-up.

[0024] In the above invention (Invention 1), it is preferable to have a membrane degassing device in a stage upstream of the sample water sampling position in the water passage of the water treatment process (Invention 2).

[0025] According to this invention (Invention 2), the concentration of hydrogen peroxide in the sample water can be calculated more accurately by degassing the sample water in advance using a membrane degassing device.

[0026] The present invention also provides a second method for measuring the concentration of hydrogen peroxide in sample water sampled at a predetermined position in a water passageway of a water treatment process, comprising: a sample water sampling step of sampling sample water at a predetermined position in the water passageway of the water treatment process; a route selection step of supplying the sample water to either a first route, which is switchably provided between a hydrogen peroxide decomposition flow path having a hydrogen peroxide decomposition means and a first circulation flow path, or a second route, which is switchably provided between a dissolved oxygen concentration measurement flow path having a dissolved oxygen concentration measurement means and the first circulation flow path; The present invention provides a method for measuring the concentration of hydrogen peroxide, comprising: a sample water measurement step of introducing sample water, measuring the dissolved oxygen concentration in the sample water with a dissolved oxygen concentration measurement means, and then passing the sample water through a hydrogen peroxide decomposition means and discharging the sample water as is; a treated water measurement step of introducing sample water into the second path in the path selection step, treating it with the hydrogen peroxide decomposition means to obtain treated water, and then introducing the treated water into the dissolved oxygen concentration measurement means to measure the dissolved oxygen concentration in the treated water; and a calculation step of calculating the hydrogen peroxide concentration in the sample water from the dissolved oxygen concentrations in the sample water and the treated water (Invention 3).

[0027] According to this invention (Invention 3), in the sample water measurement step, the dissolved oxygen concentration in the sample water is measured using a dissolved oxygen concentration measuring means, and then the sample water is passed through a hydrogen peroxide decomposition means and discharged. The flow path is then switched, and the sample water treated by the hydrogen peroxide decomposition means (treated water) is introduced into the dissolved oxygen concentration measuring means, where the dissolved oxygen concentration in the treated water is measured. The hydrogen peroxide concentration in the sample water can then be calculated from the measured dissolved oxygen concentrations in the sample water and the treated water. This enables measurement of the hydrogen peroxide concentration in the sample water with a stable start-up and using a small amount of sample water.

[0028] In the above invention (Invention 3), it is preferable to have a step of degassing the sample water before the sample water collection step (Invention 4).

[0029] According to this invention (Invention 4), the concentration of hydrogen peroxide in the sample water can be calculated more accurately by degassing the sample water in advance in the degassing step.

[0030] According to the present invention, a single dissolved oxygen concentration meter can be used to measure the dissolved oxygen concentration of sample water and that of sample water treated with a hydrogen peroxide decomposition means (treated water) without having to split the sample water and supply it separately.The hydrogen peroxide concentration in the sample water can be calculated from the dissolved oxygen concentrations of the sample water and the treated water, providing a hydrogen peroxide concentration measurement system that uses a small amount of sample water and has a stable start-up.

[0031] FIG. 1 is a configuration diagram of a hydrogen peroxide concentration measurement system according to one embodiment of the present invention. FIG. 2 is a schematic diagram illustrating a process for measuring the dissolved oxygen concentration of sample water in the embodiment. FIG. 3 is a schematic diagram illustrating a process for measuring the dissolved oxygen concentration of treated water in the embodiment. FIG. 4 is a schematic diagram illustrating a process for measuring the dissolved oxygen concentration of sample water using a conventional hydrogen peroxide concentration measurement system. FIG. 5 is a schematic diagram illustrating a process for measuring the dissolved oxygen concentration of treated water using a conventional hydrogen peroxide concentration measurement system. FIG. 6 is a schematic diagram illustrating a process for measuring the dissolved oxygen concentration of sample water using the hydrogen peroxide concentration measurement system of Patent Document 1. FIG. 7 is a schematic diagram illustrating a process for measuring the dissolved oxygen concentration of treated water using the hydrogen peroxide concentration measurement system of Patent Document 1. FIG. 8 is a schematic diagram illustrating a process for measuring the dissolved oxygen concentrations of sample water and treated water using the hydrogen peroxide concentration measurement system of Patent Document 2. FIG. 9 is a schematic diagram illustrating a measurement process for correcting the dissolved oxygen concentration of sample water using the hydrogen peroxide concentration measurement system of Patent Document 2. FIG. 10 is a schematic diagram illustrating a measurement process for correcting the dissolved oxygen concentration of treated water using the hydrogen peroxide concentration measurement system of Patent Document 2.

[0032] An embodiment of the present invention will be described below with reference to Figures 1 to 3. However, the present invention is not limited to this embodiment.

[0033] [Hydrogen Peroxide Concentration Measurement System] Figure 1 is a schematic diagram showing the configuration of a hydrogen peroxide concentration measurement system according to one embodiment of the present invention. In Figure 1, the hydrogen peroxide concentration measurement system includes a water passage 2 connected to a supply source 1 of treated water (sample water) W in a water treatment process. The water passage 3 is connected to a sample water collection tube 3 at a predetermined location. The sample water collection tube 3 branches into a first path 4 and a second path 5. A first three-way valve 6 is provided along the first path 4 as a switching means, allowing the first three-way valve 6 to switch between a dissolved oxygen concentration measurement flow path 7 having a dissolved oxygen concentration meter 8 as a dissolved oxygen concentration measurement means and a first circulation flow path 9. A second three-way valve 10 is provided along the second path 5 as a switching means, allowing the second three-way valve 10 to switch between a hydrogen peroxide decomposition flow path 11 having a catalyst resin column 12 as a hydrogen peroxide decomposition means and a second circulation flow path 13.

[0034] A third three-way valve 15 is provided at the end of dissolved oxygen concentration measurement flow path 7, and can be switched between exhaust pipe 14 and second circulation flow path 13. Furthermore, a fourth three-way valve 16 is provided at the end of hydrogen peroxide decomposition flow path 11, and can be switched between exhaust pipe 14 and first circulation flow path 9.

[0035] By switching the first three-way valve 6, the second three-way valve 10, the third three-way valve 15, and the fourth three-way valve 16, it is possible to switch whether the sample water W flows continuously from the dissolved oxygen concentration meter 8 to the catalyst resin column 12, or from the catalyst resin column 12 to the dissolved oxygen concentration meter 8.

[0036] The dissolved oxygen concentration meter 8, which serves as a dissolved oxygen concentration measuring means, is adjusted to minimize error within a predetermined flow rate range, so it is preferable to adjust the flow rate within that range. Therefore, a flow meter may be provided downstream of the dissolved oxygen concentration meter. It is also preferable to calibrate the dissolved oxygen concentration meter 8 before use.

[0037] The catalytic resin column 12 is preferably filled with a catalytic metal support (platinum group metal catalyst) carrying a platinum group metal. Hydrogen peroxide in the water to be treated (sample water) W is brought into contact with the platinum group metal catalyst, and the hydrogen peroxide can be decomposed by catalytic decomposition. The platinum group metal catalyst is supported on, for example, an anion exchanger. The anion exchanger may be a granular anion exchange resin.

[0038] [Method for Measuring Hydrogen Peroxide Concentration] Next, a method for measuring hydrogen peroxide concentration according to this embodiment using the hydrogen peroxide concentration measurement system described above will be described.

[0039] (Sample Water Sampling Step and Pathway Selection Step) First, treated water (sample water) W from the water treatment process is sampled from the sample water sampling pipe 3 connected to the water passage 2. The sampled sample water W is selectively supplied to either the first path 4 or the second path 5 by closing either the first path 4 side of the first three-way valve 6 or the second path 5 side of the second three-way valve 10.

[0040] 2 , in the sample water measurement process, first three-way valve 6 opens first path 4 and dissolved oxygen concentration measurement flow path 7 while closing first circulation flow path 9, second three-way valve 10 closes second path 5 while opening hydrogen peroxide decomposition flow path 11 and second circulation flow path 13. Third three-way valve 15 opens dissolved oxygen concentration measurement flow path 7 and second circulation flow path 13 while closing discharge pipe 14, and fourth three-way valve 16 opens hydrogen peroxide decomposition flow path 11 and discharge pipe 14 while closing first circulation flow path 9.

[0041] In this state, when sample water W collected through sample water sampling tube 3 is supplied, second three-way valve 10 closes second path 5, so the sample water W flows through first path 4, passes through first three-way valve 6, and enters dissolved oxygen concentration measurement flow path 7, where the dissolved oxygen concentration (M1) of the sample water W is measured by dissolved oxygen concentration meter 8. The sample water W then reaches third three-way valve 15, which is provided at the end of dissolved oxygen concentration measurement flow path 7. At this time, third three-way valve 15 opens the dissolved oxygen concentration measurement flow path 7 and the second circulation flow path 13, while closing the discharge pipe 14, so the sample water W flows through second circulation flow path 13 and reaches second three-way valve 10. The treated water W1 then flows through second three-way valve 10 into hydrogen peroxide decomposition flow path 11, where the hydrogen peroxide is decomposed in catalytic resin column 12. After this, treated water W1 reaches fourth three-way valve 16 located at the end of hydrogen peroxide decomposition flow path 11. At this time, fourth three-way valve 16 is open on the side facing discharge pipe 14 and closed on the side facing first circulation flow path 9, so treated water W1 is discharged from discharge pipe 14 to the outside of the system. In this manner, the dissolved oxygen concentration (M1) of the sample water W is measured.

[0042] 3 , in the sample water measurement process, first three-way valve 6 opens dissolved oxygen concentration measurement flow path 7 and first circulation flow path 9 while closing first path 4, second three-way valve 10 opens second path 5 and hydrogen peroxide decomposition flow path 11 while closing second circulation flow path 13, third three-way valve 15 opens dissolved oxygen concentration measurement flow path 7 and exhaust pipe 14 while closing second circulation flow path 13, and fourth three-way valve 16 opens hydrogen peroxide decomposition flow path 11 and first circulation flow path 9 while closing exhaust pipe 14.

[0043] In this state, when sample water W collected through sample water sampling tube 3 is supplied, first three-way valve 6 closes first path 4, so the sample water W collected through sample water sampling tube 3 flows through second path 5, passes through second three-way valve 10, and enters hydrogen peroxide decomposition flow path 11. After being treated in catalyst resin column 12, treated water W1 reaches fourth three-way valve 14 at the end of hydrogen peroxide decomposition flow path 11. At this time, fourth three-way valve 14 is closed on the side of discharge pipe 14 and open on the side of first circulation flow path 9, so treated water W1 flows through first circulation flow path 9 and reaches first three-way valve 6. From first three-way valve 6, the treated water W1 flows into dissolved oxygen concentration measurement flow path 7, and the dissolved oxygen concentration of treated water W1 is measured by dissolved oxygen concentration meter 8. The treated water W1 then reaches third three-way valve 15 at the end of dissolved oxygen concentration measurement flow path 7. At this time, the third three-way valve 15 is open on the discharge pipe 14 side and closed on the second circulation flow path 13 side, so that the treated water W1 is discharged to the outside of the system through the discharge pipe 14. In this way, the dissolved oxygen concentration (M2) of the treated water W1 is measured.

[0044] (Calculation Step) The hydrogen peroxide concentration in the sample water W is calculated from the measured dissolved oxygen concentration M1 of the sample water W and the dissolved oxygen concentration M2 of the treated water W1 as follows. That is, first, the hydrogen peroxide contained in the sample water W introduced into the catalyst resin column 12 is decomposed as shown in the following formula (1). Then, the generated oxygen dissolves in the water and becomes dissolved oxygen. 2H ２ O ２ → 2H ２ O + O ２ ...(1)

[0045] Here, the difference in the dissolved oxygen concentration values ​​between the treated water W1 and the sample water W is (M2-M1), so the hydrogen peroxide concentration in the sample water W can be calculated using the following formula (2): (M2-M1) x (68 / 32) (2) (Here, 68 is the molecular weight of hydrogen peroxide on the left side of formula (1) (two molecules, so double), and 32 is the molecular weight of oxygen on the right side of formula (1). The units on the left side are the same as the units of DO on the right side.)

[0046] In this embodiment, a membrane-type degassing device is provided upstream of the sample water W collection position, and a degassing process is performed before the sample water collection process, thereby reducing the dissolved oxygen concentration and other dissolved gases in the sample water W, thereby further improving the detection accuracy of the hydrogen peroxide concentration in the sample water W.

[0047] As described above, in this embodiment, a single dissolved oxygen concentration meter 8 can be used to measure the dissolved oxygen concentration M1 of the sample water W and the dissolved oxygen concentration M2 of the sample water (treated water) W1 treated in the catalyst resin column 12, without dividing the sample water W and supplying it separately. The hydrogen peroxide concentration in the sample water W can then be calculated from the dissolved oxygen concentration M1 of the sample water W and the dissolved oxygen concentration M2 of the treated water W1. This allows for a small amount of sample water W to be used, and water is constantly flowing through the catalyst resin column 12, resulting in a hydrogen peroxide concentration measurement system with a stable start-up.

[0048] While the present invention has been described above based on the above-described embodiment, various modifications are possible. For example, in the above-described embodiment, the sample water measurement step is followed by the treated water measurement step, but these steps may be performed in reverse order. Furthermore, the water treatment process equipment is not particularly limited, but is particularly suitable for pure water production equipment, ultrapure water production equipment, and other equipment that requires the quantification of trace amounts of hydrogen peroxide.

[0049] The present invention will be described in more detail with reference to the following specific examples.

[0050] Example 1 Ultrapure water adjusted to a hydrogen peroxide concentration of about 15 mg / L was introduced as sample water W into the hydrogen peroxide concentration measurement system shown in FIG. 1, and the hydrogen peroxide concentration was measured.

[0051] The ultrapure water before adjustment had a resistivity of 18.1 MΩ cm or more, fine particles with a particle size of 50 nm or more and 1000 particles / L or less, live bacteria of 1 particle / L or less, TOC (total organic carbon) of 1 mg / L or less, total silicon of 0.1 mg / L or less, metals of 1 ng / L or less, ions of 10 ng / L or less, and a water temperature of 25±2°C.

[0052] First, as shown in FIG. 2 , the first three-way valve 6 opened the first path 4 and the dissolved oxygen concentration measurement path 7, and closed the first circulation path 9. The second three-way valve 10 closed the second path 5, and opened the hydrogen peroxide decomposition path 11 and the second circulation path 13. The third three-way valve 15 opened the dissolved oxygen concentration measurement path 7 and the second circulation path 13, and closed the discharge pipe 14. The fourth three-way valve 16 opened the hydrogen peroxide decomposition path 11 and the discharge pipe 14, and closed the first circulation path 9. In this state, the sample water W was introduced from the first path 4 into the dissolved oxygen concentration meter 8 to measure the dissolved oxygen concentration (M1). The sample water W was then introduced into the catalyst resin column 12 for treatment, and the treated water W1 was then discharged from the discharge pipe 14 to the outside of the system.

[0053] Next, the three-way valves were switched as shown in Figure 3. That is, the first three-way valve 6 opened the dissolved oxygen concentration measurement flow path 7 and the first circulation flow path 9, and closed the first path 4. The second three-way valve 10 opened the second path 5 and the hydrogen peroxide decomposition flow path 11, and closed the second circulation flow path 13. The third three-way valve 15 opened the dissolved oxygen concentration measurement flow path 7 and the exhaust pipe 14, and closed the second circulation flow path 13. The fourth three-way valve 16 opened the hydrogen peroxide decomposition flow path 11 and the first circulation flow path 9, and closed the exhaust pipe 14. In this state, the sample water W was treated in the catalyst resin column 12 from the second path 5, and then the treated water W1 was flowed into the dissolved oxygen concentration measurement path 7 via the first circulation path 9, introduced into the dissolved oxygen concentration meter 8 to measure the dissolved oxygen concentration (M2), and then the treated water W1 was discharged out of the system through the discharge pipe 14.

[0054] The dissolved oxygen concentration (M1) of the sample water W and the dissolved oxygen concentration (M2) of the treated water W1 measured in this manner were stable, and the hydrogen peroxide concentration of the sample water W calculated from these values ​​was close to 15 mg / L. The flow rate of the sample water W during operation of the hydrogen peroxide concentration measurement system of Example 1 was 1 L / min, and the measurement time was 2 minutes per cycle.

[0055] Comparative Example 1 The hydrogen peroxide concentration was measured using the same sample water W as in Example 1 using the hydrogen peroxide concentration measurement system shown in FIGS.

[0056] First, as shown in Fig. 4, the first on-off valve 39 was opened and the second on-off valve 40 was closed to supply the sample water W to the first path 34, and the dissolved oxygen concentration (M1) of the sample water W was measured with the dissolved oxygen concentration meter 37. Next, as shown in Fig. 5, the first on-off valve 39 was closed and the second on-off valve 40 was opened to introduce the sample water W into the catalyst resin column 38 for treatment, and the dissolved oxygen concentration (M2) contained in this treated water W1 was measured with the dissolved oxygen concentration meter 37.

[0057] The values ​​of the dissolved oxygen concentration (M1) of the sample water W and the dissolved oxygen concentration (M2) of the treated water W1 measured in this manner took at least two minutes for the dissolved oxygen concentration (M2) of the treated water W1 to stabilize, which required time to accurately calculate the hydrogen peroxide concentration of the sample water W. This is thought to be because the water supply to the catalyst resin column 38 was initially stopped, requiring time for stabilization during startup. Furthermore, the flow rate of the sample water W during operation of the hydrogen peroxide concentration measurement system of Comparative Example 1 was 1 L / min, and the measurement time was 10 minutes per cycle.

[0058] Comparative Example 2 The hydrogen peroxide concentration was measured using the same sample water W as in Example 1 using the hydrogen peroxide concentration measurement system shown in FIGS.

[0059] 6 , first on-off valve 57 and second on-off valve 61 were opened, and first communication valve 63 and second communication valve 65 were closed. With this state, sample water W was supplied from sample water sampling tube 53 to first path 54 and second path 58, and the dissolved oxygen concentration (M1) of sample water W in first path 54 was measured with dissolved oxygen concentration meter 56. During this time, sample water W was also supplied to second path 58, passed through catalyst resin column 60, and then discharged.

[0060] 7 , first on-off valve 57 and second on-off valve 61 were closed, and first communicating pipe 62 and second communicating pipe 64 were opened. With this, sample water W was supplied from sample water sampling pipe 53 to first path 54 and second path 58. After being treated in catalyst resin column 60, sample water W in second path 58 passed through second communicating pipe 64 and was introduced into dissolved oxygen concentration meter 56 from dissolved oxygen concentration measuring section 55 of first path 53, where the dissolved oxygen concentration (M2) was measured. During this time, sample water W was also supplied to first path 54 and then discharged from discharge section 59 via first communicating pipe 62.

[0061] The values ​​of the dissolved oxygen concentration (M1) of the sample water W and the dissolved oxygen concentration (M2) of the treated water W1 measured in this manner were stable, and the hydrogen peroxide concentration of the sample water W calculated from these values ​​was approximately 15 mg / L, similar to that of Example 1. Furthermore, the flow rate of the sample water W during operation of the hydrogen peroxide concentration measurement system in Comparative Example 2 was 2 L / min, and the measurement time was 2 minutes per cycle.

[0062] Comparative Example 3 The hydrogen peroxide concentration was measured using the same sample water W as in Example 1 using the hydrogen peroxide concentration measurement system shown in FIG.

[0063] 8 , first on-off valve 76 and second on-off valve 80 were opened, and communication valve 82 was closed. With sample water W supplied from sample water collection tube 73 to first path 74 and second path 77, the dissolved oxygen concentration M1 of sample water W in first path 74 was measured by first dissolved oxygen concentration meter 75. In addition, sample water W in second path 77 was treated in catalyst resin column 78, and the dissolved oxygen concentration M2 of this treated water W1 was measured by second dissolved oxygen concentration meter 79.

[0064] The values ​​of the dissolved oxygen concentration (M1) of the sample water W and the dissolved oxygen concentration (M2) of the treated water W1 measured in this manner were stable, but the hydrogen peroxide concentration of the sample water W calculated from these values ​​had a larger error than in Example 1, Comparative Example 1, and Comparative Example 2. This is thought to be due to an error between the first dissolved oxygen concentration meter 75 and the second dissolved oxygen concentration meter 79. Furthermore, the flow rate of the sample water W during operation of the hydrogen peroxide concentration measurement system in Comparative Example 3 was 2 L / min, and the measurement time was 1 min / cycle.

[0065] In Comparative Example 3, as shown in Figures 9 and 10, sample water W was supplied simultaneously to both the first dissolved oxygen concentration meter 75 and the second dissolved oxygen concentration meter 79, and treated water W1 was also supplied simultaneously.The accuracy of calculating the hydrogen peroxide concentration could be improved by correcting the errors between the first dissolved oxygen concentration meter 75 and the second dissolved oxygen concentration meter 79 based on the difference in the measured values ​​between them.However, in this case, the measurement time for the sample water W required to operate the hydrogen peroxide concentration measurement system in Comparative Example 3 was approximately three times longer.

[0066] Table 1 shows the flow rate of the sample water W, the measurement time, and the number of constituent devices (number of catalyst resin columns + number of dissolved oxygen concentration meters) in Example 1 and Comparative Examples 1 to 3.

[0067]

[0068] As is clear from Table 1, the hydrogen peroxide concentration measurement system of Example 1 not only has a small flow rate of the sample water W and a small measurement time, but also has a small number of constituent devices, making it the most comprehensively superior system.

[0069] REFERENCE SIGNS LIST 1 Source of treated water (sample water) W for treatment process 2 Water passage 3 Sample water sampling pipe 4 First path 5 Second path 6 First three-way valve 7 Dissolved oxygen concentration measurement flow path 8 Dissolved oxygen concentration meter (dissolved oxygen concentration measurement means) 9 First circulation flow path 10 Second three-way valve 11 Hydrogen peroxide decomposition flow path 12 Catalytic resin column (hydrogen peroxide decomposition means) 13 First circulation flow path 14 Discharge pipe 15 Third three-way valve 16 Fourth three-way valve

Claims

1. A hydrogen peroxide concentration measurement system for measuring the hydrogen peroxide concentration in sample water collected at a predetermined position in a water passage of a water treatment process, comprising: a sample water collection tube for collecting the sample water; the sample water collection tube branching into a first path and a second path, the first path being switchably provided with a dissolved oxygen concentration measurement flow path having a dissolved oxygen concentration measurement means and a first circulation flow path, the second path being switchably provided with a hydrogen peroxide decomposition flow path having a hydrogen peroxide decomposition means and a second circulation flow path, the hydrogen peroxide decomposition flow path being switchably branched into a discharge pipe and the first circulation flow path, while the dissolved oxygen concentration measurement flow path being switchably branched into a discharge pipe and the second circulation flow path, and it is possible to change whether the sample water flows continuously from the dissolved oxygen concentration measurement means to the hydrogen peroxide decomposition means, or from the hydrogen peroxide decomposition means to the dissolved oxygen concentration measurement means.

2. A hydrogen peroxide concentration measurement system as described in claim 1, further comprising a membrane degassing device disposed upstream of a sample water sampling position in a water passage for the water treatment process.

3. A method for measuring the hydrogen peroxide concentration in sample water collected at a predetermined position in a water passage of a water treatment process, comprising: a sample water collecting step of collecting sample water at a predetermined position in the water passage of the water treatment process; a route selecting step of supplying the collected sample water to either a first route in which a hydrogen peroxide decomposition flow path having a hydrogen peroxide decomposition means and a first circulation flow path are switchable, or a second route in which a dissolved oxygen concentration measurement flow path having a dissolved oxygen concentration measurement means and the first circulation flow path are switchable; a sample water measuring step of introducing sample water to the first route side in the route selecting step, measuring the dissolved oxygen concentration in the sample water with the dissolved oxygen concentration measurement means, and then passing the sample water through the hydrogen peroxide decomposition means and discharging it; and a treated water measuring step of introducing sample water to the second route side in the route selecting step, treating the sample water with the hydrogen peroxide decomposition means to obtain treated water, and then introducing the treated water into the dissolved oxygen concentration measurement means to measure the dissolved oxygen concentration in the treated water. a calculation step of calculating the hydrogen peroxide concentration in the sample water from the dissolved oxygen concentrations in the sample water and the treated water.

4. The method for measuring the concentration of hydrogen peroxide according to claim 3, further comprising a step of degassing the sample water prior to said step of collecting the sample water.

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